The present invention relates to a multiple-function convertor for converting electric signals to vibration of vibrating plates mounted in a case of a portable instrument such as the portable telephone and the beeper, and more particularly to a convertor for converting electric input signals to vibration of a vibrating plate to generate sounds and to vibrate the case of the portable instrument to inform the user of the instrument about the receiving of calling signals.
In recent years, there is provided a portable telephone having a multiple-function convertor for vibrating a vibrating plate to generate sounds, and to further generate voices of the caller. Therefore, such a multiple-function convertor can be used in the hands free operation in which the vibration plate is operated as a speaker for the voice of the caller and as a microphone for the voice of the user.
FIG. 3 is a plan view showing a conventional multiple-function convertor in which a vibrating plate is removed in order to show an internal composition, and FIG. 4 is a sectional view taken along a line IV-IV of FIG. 3.
Referring to FIG. 3, the multiple-function convertor comprises a case 1, and a magnetic circuit composition 8 provided in the case 1. The magnetic circuit composition 8 comprises a yoke 4, a magnet 5 mounted on the yoke 4 and a top plate 6.
The yoke 4 is supported by an annular supporting spring plate 7. The supporting spring plate 7 comprises an outer annular plate 7a, an inner annular plate 7b and connecting plates 7c connecting both plate 7a and 7b with each other. The inner annular plate 7b is fixed to a top of a cylindrical projection 4a of the yoke 4 by welding, and the outer annular plate 7a is embedded in an inside annular projection la of the case 1. Thus, the magnetic circuit composition 8 is hung in the case 1 and resiliently supported by the connecting plates 7c. A vibrating plate 2 made of plastic is secured to the annular projection 1a of the case 1 by an adhesive at a periphery thereof. An annular voice coil 3 is secured to the underside of the vibrating plate 2. The voice coil 3 is disposed in an annular magnetic gap 9 formed between the cylindrical projection 4a and the top plate 6.
When an alternating current driving signal is applied to the voice coil 3, an alternating electromagnetic force generates between the voice coil 3 and the magnetic circuit composition 8.
When the frequency of the driving signal is high and in the range of the audio frequency, the vibrating plate 2 is vibrated to generate sounds such as beeping sounds or voices. On the other hand, the magnetic circuit composition 8 supported by the supporting spring plate 7 does not vibrate since the magnetic circuit composition has a small natural frequency.
To the contrary, when the frequency of the driving signal is low and in a frequency range lower than the audio frequency, the vibrating plate 2 does not so largely vibrate as to generate sounds, and the magnetic circuit composition 8 vibrates without generating sounds. The vibration of the magnetic circuit composition 8 is transmitted to the body of the portable instrument through the case 1, thereby informing the user of the instrument about the receiving of calling signals by the vibration.
In the case that the magnetic circuit composition 8 vibrates at a low frequency signal, it may occur that the vibrating plate 2 approaches to the magnetic circuit composition during the vibrating of the vibrating plate 2 and collides with the magnetic circuit composition 8, which may generate abnormal sounds and cause parts of the convertor to deform and break.
In order to prevent such troubles from occurring, it is necessary to increase the gap between the vibrating plate 2 and the magnetic circuit composition 8, which means that the thickness of the convertor can not be reduced more than a certain limitation.
In addition, the operation of the convertor is either of the sound generating vibration and vibration without sound, and both vibrating operations cannot be carried out at the same time.
An object of the present invention is to provide a multiple-function convertor which can be reduced in thickness without causing collision between members therein.
Another object of the present invention is to provide a multiple-function convertor which can be operated to generate sounds and vibration of instruments at the same time.
According to the present invention, there is provided a multiple-function convertor for a portable electronic instrument, comprising a case for mounting components of the electronic instrument, a vibrating plate securely mounted in the case at one of axial ends of the case, an annular first coil secured to the vibrating plate, a magnetic circuit composition mounted in the case, the magnetic circuit composition comprising a yoke having a flange and a core formed on the flange, an annular magnet mounted on the flange of the yoke at one of magnetic poles thereof, and a top plate comprising an annular portion and a cylindrical portion projected from a peripheral portion of the annular portion, the annular portion being engaged with the other magnetic pole of the magnet, supporting means for resiliently supporting the magnetic circuit composition in the case, a coil holding plate secured to the case at the other axial end of the case, an annular second coil secured to the coil holding plate, the first coil being inserted in a first magnetic gap formed in the magnetic circuit composition at one of axial end sides thereof, and the second coil being inserted in a second magnetic gap formed in the magnetic circuit composition at the other axial end side thereof, and means for independently applying electric exciting current to the first coil and second coil.
The cylindrical portion of the top plate is provided for surrounding the periphery of the magnet.
The supporting means comprises a pair of annular supporting spring plates one of which is secured between a base of the cylindrical portion of the top plate and the case, and the other of which is secured between an end portion of the cylindrical portion and the case.